Provide examples for guidance on using heading levels in a dialog

[gurooprasad]

Below is the update provided in the comment posted by mcking65

After discussion in the February 12, 2018 meeting, there is an agreement that the dialog titles could be either H1 or H2.
Some members point out there could also be circumstances where H3+ could be appropriate.

We concluded:

• It is helpful if there is a consistent approach across dialogs in an application.
• There is not necessarily a need for the APG to prescribe a specific approach.

Based on the above comment, if there is no need to prescribe a specific approach, we should at least provide some examples. Those examples should provide guidance to decide when to use H1 and non H1 heading levels.

[gurooprasad]

This issue is getting tagged to WCAG intro. So closing this one and reopening original issue #551 for better referencing.